Electroplating current conductor



Oct. 22, 1957 M. vRlLAKAs ET AL 2,810,691

ELECTRORLATING CURRENT CONDUCTOR Filed Nov. 17, 1951 4 INVENTOR A749605 V/A/ JOHN VP/Lilii United States Patent O i ELECTROPLATING CURRENT CONDUCTOR Marcus Vrilakas and John Vrilakas, Sacramento, Calif.

Application November 17, 1951, Serial No. 256,892 4 Claims. (Cl. 20d-212) The invention relates to means for electroplating objects and particularly to devices for electroplating conducting objects of a rotatable nature, such as internal combustion engine crank shafts. A process and structure related to the present apparatus are disclosed in the copending application of Marcus Vrilakas entitled Method and Apparatus for Selective Plating, filed October 27, 1951, with Serial Number 253,526, now Patent No. 2,710,834. The present invention is related primarily to mechanism useful for conducting the electroplating current to or through the rotatable object to be plated while it is immersed in the plating bath.

Considerable difficulty has been encountered in the past in endeavoring to conduct a relatively heavy electroplating current between a rotating object in the plating bath such as a crank shaft and the electrical current leads. Ordinary brush or mechanical contact devices seem to develop wear and other difficulties very rapidly. In commercial production, the life of conducting brushes or comparable devices is entirely too short. In addition, there is difficulty in establishing a good conducting relationship between a stationary member and a rotary member beneath the surface of the electrolyte or plating bath. Even though satisfactory conditions can be established initially, the usual effect of the plating bath is to cause a rapid deterioration and sometimes an actual failure of the current conducting properties of the relatively moving parts. p

It is therefore an object of our invention to obviate the foregoing difficulties and in general to provide an improved mechanism in the nature of an electroplating current conductor effective for use in electroplating submerged rotating conducting bodies.

Another object of our invention is to provide means for conducting a relatively heavy electroplating current into a submerged rotating and conducting body.

A still further object of our invention is to provide a means for improving the lasting qualities of a conductor effective between a rotating and a non-rotating member.

Other objects of our invention, together with the foregoing, are attained in the embodiment of the device described in the accompanying description and illustrated in the accompanying drawing in which The figure is partially diagrammatic and has portions broken away to reduce its size but illustrates, largely in cross section, an electroplating tank in which the electroplating current conductor of our invention is utilized in connection with a rotating crank shaft being electroplated.

The device of our invention is susceptible to numerous variations and modifications depending upon the especial service to which it is to be put and depending furthermore upon the environment in which it is to operate. In the present instance, it is utilized in connection with an electroplating tank 6 utilized to confine an open surfaced body 7 or bath of electroplating liquid such as a suitable electrolyte for chromium plating, for example.

Situated within and beneath the surface of the bath 7 is ICC a support 8 usually externally mounted but shown as secured to the tank 6 and separated from it electrically by an insulating pad 9. There is no electrical connection between the support 8 and the tank. The support is conveniently fabricated of a metal shell 11 within which a pair of plastic bearings 12 and 13 are disposed. These are fabricated of any convenient material, that known as Lucite (methyl methacrylate) being quite satisfactory. The Lucite bearings 12 and 13 are held in position against a central annular shoulder 14, defining a chamber, by cap plates 16 and 17 which are removable so that the device can be assembled and disassembled. A pipe plug 18 is normally positioned to close the central chamber. When the mechanism is not in operation, the plug 18 can be removed from its opening and a current of flushing liquid can be run by force through the support bearings 12 and 13.

Adapted to revolve in the bearings is a support shaft 21 having an axis 22 disposed in a generally horizontal plane below the surface of the plating bath. One end of the shaft 21 carries a flange coupling 23 adapted to rotate with the shaft and designed to be joined temporarily to the mating driving flange 24 of an electrically conducting and rotatable crank shaft 26. The crank shaft is connected in an electric circuit by another connector not shown but similar to the one shown herein and is adapted to be revolved about the axis 22 by well known and standard rotating mechanism.

At the other end of the shaft 21 we provide a housing 27 held on a support 28 disposed beneath the surface of the bath 7 and usually externally mounted but shown as supported on but separated by an insulator 29 from the wall of the tank 6. The housing 27 is provided with a removable cover 31. The housing and the cover are so contoured that they form a central chamber 32 concentric with the axis 22.. Situated within the chamber so formed is a conducting disc 33 held by a fastening 34 on one end of the shaft 21 and designed to rotate in unison therewith by a suitable key or other structure not shown in detail. A pair of Lucite rubbing blocks 36 and 37 are disposed within the chamber 32 and serve as locating and supporting devices.

Confined within the chamber 32 is a pool 38 of a liquid electrical conductor such as mercury. This is introduced through a filler neck 39 carrying a plug 41. When the electrolyte bath 7 is not present, the mercury can be introduced and the opening in the filler neck plugged, following which the entire tank can be filled with electrolyte. The mercury serves as a conductor of elec troplating current between the casing cover 31 and the casing 27 and the disc 33. Current iiow from the disc is through the shaft 21 and the flange 23 to the crank shaft 26. The current is led into this portion of the structure (as distinguished from the remainder of the circuit, not shown, connected to the crank shaft 26) by any suitable means such as an electrical lead 42 fastened to a metallic conducting tube 43 joined to the casing 27. By this means current flowing through the conductor 42 and through the tube 43 is carried to the housing 27 and its cover 31 and then flows through the mercury into the rotating disc 32 by a firm, continuous metallic path. Current fiow is then through the shaft 21 into the crank shaft 26 and back through a return portion of the circuit, not illustrated.

The foregoing mechanism provides an excellent conducting path despite rotation of the crank shaft 26 and the shaft 21 with respect to the remainder of the structure. It may happen, however, that the pressure or head of the electrolyte bath 7 is sufficient to force electrolyte to enter into the chamber 32 and to cause deposits, or corrosion or other deleterious chemical action. To avoid this, we provide first a packing or sealing device 51 extending between the casing 27 and the shaft 21, being held in adjusted location and with the requisite amount of compression by a packing gland S2 adjustably secured by screw devices.

Even so, this packing alone is sometimes not suicient. We therefore provide, in addition, a hydrostatic pressure within the chamber 32 and upon the mercury 38 greater than that due to the electrolyte bath '7. The tube 43 is extended to an upstanding end 54 higher than the level of the electrolyte 7. The tube contains Eiquid, such as water, at the higher level. The water not only fills the tube 43 but likewise occupies the upper space within the cavity or chamber 32 not occupied by the mercury and between the mercury and the packing 51. The connection 56 of the tube to the casing 27 is at such a location that any air which might otherwise be entrapped within the housing escapes as the water flows in to displace it. When the tube 43 is full, any leakage past the packing 5l is necessarily from the interior of the chamber 32 into the electrolyte bath 7 and not otherwise. The leaking material is necessarily water and not mercury. The minor dilution of the electrolyte by any outwardly leaking water is entirely immaterial. The only substances in Contact with the interior portion of the chamber 27 and its cover 32 are water and mercury. These do not produce any deleterious, long term effects.

ln accordance with our invention, therefore, we have provided an electroplating current conductor normally submerged below the level of a plating bath and effective to carry relatively heavy electroplating current from a stationary member into a rotating7 conducting member. The current is conducted in part through a pool of mercury, that mercury being subjected to a hydrostatic pressure or head somewhat in excess of that due to the eiectroplating bath itself. We therefore have aiforded a new and improved mechanism which substantially attains all of the objects of our invention.

What is claimed is:

l. An electroplating current conductor comprising a tank for containingl an electroplating bath at a predetermined level open to the atmosphere, a rotatable shaft in said tank below said level of said bath for supporting a rotatable conducting obj'ect to be electroplated, a stationary housing insulated from said tank and disposed in said tank below said level of said bath and subject to the hydrostatic pressure of said bath, a conducting disc in said housing and secured to said shaft, a pool of conducting liquid in said housing in contact with said disc, means for conducting electroplating current to said housing, means tor supporting a liquid column open to the atmosphere and open to the interior of said housing liqud'supeiort'o the hydrostatic pressure of said bath',

and a seal for inhibiting leakage between said housing and said shaft.

2. An electroplating current conductor comprising a housing having a chamber, a shaft rotatable within said housing, means for subjecting the exterior of said housing and said shaft to a predetermined hydrostatic pressure, a disc on said shaft and disposed within said chamber, means within said chamber for conducting current between said housing and said disc, and a tube connected to said chamber and Lextending upwardly therefrom, said tube having an atmospheric opening at a point above a liquid column in -said tube of a height subjecting said chamber to an internal hydro-static pressure greater than said predetermined hydrostatic external pressure on said housing and on said shaft.

3. An electroplating current conductor comprising a shaft, means for mounting said shaft for rotation about an axis, a disc at one end of said shaft, a housing encompassing said disc, means for preventing rotation of said housing about said axis, mercury in said housing in contact with said disc, means for immersing said housing and said shaft in a plating bath and thereby subjecting said housing and shaft to exterior hydrostatic pressure, means for supplying water to said housing at an interior hydrostatic pressure greater than said exterior hydrostatic pressure, and means for conducting an electroplatsubmerged in said bath,

ing current through said mercury.

4. An electroplating current conductor comprising a tank for containing an electroplating bath at a predetermined level, said tank being open to the atmosphere, a shaft in said tank disposed below said level to be a stationary housing insulated from said tank and disposed in said tank below said level to be submerged in said bath, a conducting disc in said housing and secured to said shaft, a pool of conducting liquid in said housing in contact with said disc, a single water conduit connected into said housing and ending above said level of said bath, means for conducting electroplating current to said housing through said conduit, and a seal for inhibiting leakage between said housing and said shaft.

References Cited in the le of this patent UNITED 'STATES PATENTS 1,433,331 Angstrom Oct. 24, 1922 2,044,180 Newton June 16, 1936 2,315,272 Potthoft Mar. 30, 1943 2,322,796 Fentress June 29, 1943 2,542,056 Ravenscroft Feb. 20, 1951 

1. AN ELECTROPLATING CURRENT CONDUCTOR COMPRISING A TANK FOR CONTAINING AN ELCTROPLATING BATH AT A PREDETERMINED LEVEL OPEN TO THE ATMOSPHERE, A ROTATABLE SHAFT IN A TANK BELOW SAID LEVEL OF SAID BATH FOR SUPPORTING A ROTATABLE CONDUCTING OBJECT TO BE ELECTROPLATED, A STATIONARY HOUSING INSULATED FROM SAID TANK AND DISPOSED IN SAID TANK BELOW SAID LEVEL OF SAID BATH AND SUBJECT TO THE HYDROSTATIC PRESSURE OF SAID BATH, A CONDUCTING DISC IN SAID HOUSING AND SECURED TO SAID SHAFT, A POOL OF CONDUCTING LIQUID IN SAID HOUSING IN CONTACT WITH SAID DISC, MEANS FOR CONDUCTING ELECTROPLATING CURRENT TO SAID HOUS- 